Observations

Description

Valves are linear-elliptical with rostrate, subrostrate or narrowly subcapitate apices. The raphe valve has a linear axial area and transversely rectangular central area. The rapheless valve has a narrow, linear axial area. The asymmetric central area on the rapheless valve contains a shallow depression on the internal valve surface. The raphe is straight with expanded external proximal endings. The striae are radiate throughout both valves.

Valves are linear-elliptical with rostrate, subrostrate or narrowly subcapitate apices. The raphe valve has a linear axial area and transversely rectangular central area. The rapheless valve has a narrow, linear axial area. The asymmetric central area on the rapheless valve contains a shallow depression on the internal valve surface.

Compare

Planothidium dubium is similar in size and shape to P. rostratum, but differs from it by the absence of the hood on rapheless valve. It differs from P. lanceolatum, which also has a depression on the asymmetric central area of the rapheless valve and by the rostrate to subcapitate valve apices.

Links & ID's

Index Nominum Algarum (INA)

California Academy of Sciences (CAS)

North American Diatom Ecological Database (NADED)

NADED ID: 155021

Autecology Discussion

Habits

Size Range

101-1000 µm3 (ie Amphora veneta)

Motility

slightly motile (e.g. Cocconeis)

Attachment

unattached

Habitat

benthic

Colony

solitary

EMAP Assessment

The Environmental Protection Agency (EPA) western Environmental Monitoring and Assessment Program (EMAP) study was completed during the years 2000-2004 (see citations at bottom of this page). Over 1200 streams and rivers in 12 western states (Arizona, California, Colorado, Idaho, Montana, Nevada, North Dakota, Oregon, South Dakota, Utah, Washington and Wyoming) were selected for sampling based on a stratified randomized design. This type of design insures that ecological resources are sampled in proportion to their actual geographical presence. Stratified randomized design also allows for estimates of stream length with a known confidence in several “condition classes” (good or least-disturbed, intermediately-disturbed, and poor or most-disturbed) for biotic condition, chemistry and habitat.

EMAP Distribution

Planothidium dubium

Distribution

The distribution map represents the relative abundance of this Planothidium dubium in the western EMAP study. Relative abundance is a measure of the proportion of cells of this species based on a "fixed count" of 300 total diatom cells counted and identified. Each of the western EMAP sample sites is shown, either with a black dot for sites where Planothidium dubium was not recorded, or with a red circle indicating the relative abundance of Planothidium dubium.

Note that the size of the proportional symbols varies between species to help show both abundant and rare species.

Scale for the map to the left

EMAP Response Plots

Planothidium dubium

Responses

The 15 response plots show an environmental variable (x axis) against the relative abundance (y axis) of Planothidium dubium from all the stream reaches where it was present. Note that the relative abundance scale is the same on each plot. Explanation of each environmental variable and units are as follows:

ELEVATION = stream reach elevation (meters)STRAHLER = distribution plot of the Strahler Stream Order SLOPE = stream reach gradient (degrees)W1_HALL = an index that is a measure of streamside (riparian) human activity that ranges from 0 - 10, with a value of 0 indicating of minimal disturbance to a value of 10 indicating severe disturbance.PHSTVL = pH measured in a sealed syringe sample (pH units)log_COND = log concentration of specific conductivity (µS/cm)log_PTL = log concentration of total phosphorus (µg/L)log_NO3 = log concentration of nitrate (µeq/L)log_DOC = log concentration of dissolved organic carbon (mg/L)log_SIO2 = log concentration of silicon (mg/L)log_NA = log concentration of sodium (µeq/L)log_HCO3 = log concentration of the bicarbonate ion (µeq/L)EMBED = percent of the stream substrate that is embedded by sand and fine sedimentlog_TURBIDITY = log of turbidity, a measure of cloudiness of water, in nephelometric turbidity units (NTU).DISTOT = an index of total human disturbance in the watershed that ranges from 1 - 100, with a value of 0 indicating of minimal disturbance to a value of 100 indicating severe disturbance.